1. Field of the Invention
The present invention relates to a start control apparatus for inhibiting self-ignition at the time of starting an internal combustion engine.
2. Description of the Related Art
There has been known technique of improving exhaust emission by continuously executing an ignition control even after operating so as to stop an internal combustion engine, and stopping the ignition control after completely burning fuel in a cylinder (refer to JP 5-312083 A). In addition, JP 2002-4985 A, JP 2001-173488 A, and JP 10-227236 A exist as prior art documents relevant to the present invention.
In a so-called cylinder direct injection type engine in which fuel is directly injected into each cylinder, since a fuel injection having comparatively high penetration force is executed, the fuel tends to be attached to a wall surface in the cylinder. Further, when the attached fuel is vaporized during an engine stop, there is a possibility that an air-fuel mixture having a high concentration of combustible gas is generated in the cylinder. In particular, in the case where the engine is stopped after a high load operation, the engine is stopped with keeping a high temperature. Accordingly, the attached fuel tends to be vaporized, and there is a high possibility that the air-fuel mixture in the cylinder reaches a combustible concentration. In the case where the engine is restarted in a state in which the air-fuel mixture having the high concentration of the combustible gas exists in the cylinder as mentioned above, there is a possibility that self-ignition is caused in a compression stroke at the time of cranking. Further, in the case where the temperature of the engine is high, the self-ignition tends to be caused. The self-ignition causes a starting property of the engine to be deteriorated.
Further, the self-ignition is also caused by the matter that the fuel attached to an intake port is vaporized so as to flow into the cylinder. Therefore, there is a possibility that the self-ignition is caused in an engine in which the fuel is injected to the intake port as well as the cylinder direct injection type engine.
However, in the prior art, the unburned fuel is burned only at a time while the engine is being stopped. Accordingly, even in the case of controlling the concentration of the unburned fuel in the cylinder to be less than the combustible concentration at the time of stopping the engine, the concentration of the unburned fuel reaches the combustible concentration at the time of restarting due to the vaporization of the attached fuel during the engine stop, and there is a possibility that the self-ignition is caused.